1. Field of the Invention
The present invention is related to a liquid crystal display (LCD) device, particularly to an improved type of LCD device with wide-viewing-angle and high optical transmittance.
2. Background of the Invention
The intensity of light passing through a LCD device is controlled by the alignments of liquid crystal (LC) molecules between two transparent electrodes of the device. Depending on the polarization and refraction properties of light passing through the LC molecules with different alignments, the optical transmittance and the viewing angle can be very distinct for different types of LCD devices. For the conventional twisted nematic (TN) type LCD, the device can exhibit a superior optical transmittance. However, as the effective LC birefringence has a strongly viewing angle dependent, the problem of TN type LCD is that viewing angles are very restrictive.
To overcome this problem, manufacturers have developed various type of wide-viewing-angle LCDs, such as multi-domain vertical alignment (MVA) and patterned vertical alignment (PVA) modes. The wide viewing angle of the PVA mode is achieved by using the fringe-field effect and optical compensation by retardation films. For the MVA mode, each pixel was divided into multiple domains by using protrusions or electrode (ITO) patterns on the top and bottom substrates, by which the LC molecules in different domains can be aligned to different in-plane directions, such that both the transmittance and viewing angle can be increased.
To date, the commonly used technologies for wide viewing angle are based on the vertical alignment (VA) mode. However, no matter using MVA or PVA modes, a disconnection line (or an optical dark fringe) always appears in the area near the protrusions or the electrode patterns between two adjacent domains, because at which the LC molecules are not affected by the electric field between the two electrodes. This phenomenon leads to some singular points in each pixel and, as a consequence, a deficient image quality.
Therefore, it is very important to develop a technology for LCD devices with a wide viewing angle and a high optical transmittance, but without optical dark fringes near the multi-domain boundaries in each pixel.